How many codeine pills do you need to get high?

That depends on several factors, most importantly, body weight and tolerance. If you use opioids/opiates regularly, you will need a higher dose to obtain the desired effects due to tolerance. For a non-tolerant person, the dose would be between 50 and 200mg. However, as said, the doses needed to obtain effects goes up with increased body weight.

It is also important to take note of the fact some people are allergic to codeine. If you are one of those people, even a small dose might trigger an allergic attack which might be fatal.

Keep in mind that using prescription medications that your doctor did not write for you is illegal. In most areas it is also illegal to use them other than directed, such as recreationally.